Monday, September 12, 2016

Body Parts – The Intestines

We use the term intestinal
fortitude to describe someone with “the courage to endure and go on.”Well, I have a “gut” feeling that my readers will have the intestinal fortitude to read this blog post despite these bad puns, and that you’ll have no trouble “digesting” the
information within.

At mealtime, after your cat swallows, the food goes to the
back of the throat (the pharynx), and then into the esophagus - the muscular
tube connecting the pharynx to the stomach. It then enters the stomach where
some digestion occurs, before making its way to the organ that is the focus of
our column today: the intestines.

The intestinal tract is divided into two major portions: the
small intestine and the large intestine.

When food leaves the stomach, it enters the small
intestine.The small intestine is the
longest portion of the gastrointestinal tract.Expanded end-to-end, it is approximately 3 to 4 times the length of the
cat’s body!The small intestine is
divided into three regions: the duodenum, the jejunum, and the ileum.

The duodenum is the very first part of the intestine, and
sits relatively stationary in the abdomen. The jejunum is the longest part of
the small intestine and is free to move around, often occupying whatever
unoccupied space available within the abdomen.The ileum is the short, terminal portion of the small intestine.

Digested food leaves the small intestine and enters the next
portion, the large intestine.We tend to
use the term “colon” interchangeably with “large intestine”, but this isn’t
entirely correct.The large intestine actually
includes the cecum, colon, rectum, and anal canal.The cecum is a small pouch at the junction of
the ileum and the colon.It is analogous
to our appendix.The colon has thinner
walls and is baggier than the small intestine. The last few inches of the colon
is the rectum, followed by the anal canal – the short, terminal part of the
gastrointestinal tract that is found just inside the anus. For consistency, I’ll mostly use the term
“large intestine”, but I’m mainly referring to the colon.

The small intestine is where most of the action occurs,
digestion-wise.After a little initial
digestion and processing in the stomach, food arrives in the intestine where digestive
juices from the pancreas, and bile from the gall bladder both empty into the
duodenum through small openings in the duodenum wall. These enzymes and bile
digest the food even further, breaking it down into smaller molecules which are
absorbed from the small intestine into the bloodstream. Food then passes from
the ileum to the large intestine.

The large intestine is involved in the final phase of
digestion.The bulk of the water and
electrolytes gets absorbed from the food, resulting in the formation of
feces.The feces then move into the
rectum and anal canal where it is stored until defecation occurs.

As you might imagine, there are many disorders of the feline
intestinal tract, and a discussing all of them would certainly be beyond the
scope of this column.Two common
ailments, however, warrant a mention:inflammatory bowel disease and colitis.

Inflammatory bowel disease (IBD) is a condition in which the
immune system mounts an excessive inflammatory response, sending inflammatory
cells inappropriately into the gastrointestinal tract.Any part of the GI tract- stomach, small intestine, large intestine –
may be affected, although the small intestine is most commonly affected.People mistakenly use the term “irritable
bowel syndrome” interchangeably with IBD.When inflammatory cells infiltrate the small intestine, a number of
clinical signs may be seen.The most
common are poor appetite, weight loss, vomiting, and diarrhea.These signs can occur singly, or in any combination.Making the diagnosis of IBD requires ruling
out other common causes of gastrointestinal inflammation, for example:
parasites, food allergy, and metabolic disorders such as hyperthyroidism.Routine lab tests tend to be normal in cats
with IBD. Ultimately, a definitive
diagnosis requires obtaining biopsy specimens from the intestinal tract.Corticosteroids are usually effective in
controlling IBD in cats.In fact, my own
cat, Mittens, was diagnosed with IBD three years ago, and she has been symptom-free
on medication.

Colitis is inflammation of the large intestine.Cats with colitis often have diarrhea,
occasionally with blood and/or mucus.
They show increased frequency of defecation, and may show straining to
defecate. Vomiting is a common
sign. A common cause of colitis is a
sudden change of diet. Stress is another
trigger for colitis. Cats are creatures
of habit and like to have a consistent environment. A new cat in the house, relatives visiting
over the holidays, or a change in the owner’s work schedule can stress out a
cat and induce colitis. Most cases of
colitis resolve spontaneously after a few days.
A prescription diet that is high in fiber is helpful in speeding the
recovery. Stubborn cases may require medication in addition to a therapeutic
diet.

Dr. Arnold Plotnick (MS, DVM, ACVIM) blogs about professional and personal life experiences as an expert in the field of feline veterinary medicine.

Dr. Arnold Plotnick is a board-certified veterinary internist, feline expert, and the founder of Manhattan Cat Specialists. In addition to his medical work, he is an award-winning veterinary medicine writer.